The mean-field solution of this model by D. S. Fisher (ref. 8) reads to a |ω| cusp below threshold (as long as the system exhibits hysteresis) and D. S. Fisher has given general arguments as to why the same power law should be seen in low dimensions. Experimentally, cusps in ε(ω) are observed (ref. 6) but the exact ω-dependence is not yet clear.Google Scholar